The popularity of the cellular telephone evidences the fact that modern telephone users desire to be reachable to calling parties without being restricted by physical location. Before cellular telephones were so widely available, telephone users in many areas could subscribe to a call forwarding service from their local telephone service provider. Call forwarding could be used to associate the subscriber's main number with an alternative number. When a calling party attempted to reach the subscriber, while the call forwarding service was activated, the alternative number would be rung, instead of the main number. Thus, a subscriber could enjoy the freedom to change its physical location, while maintaining some ability to receive calls that were actually made to the user's main number. The subscriber could typically forward incoming calls to any other telephone number.
Typically, there are two main classes of call forwarding services, including Switch-based and Advanced Intelligent Network (AIN) based. Switch-based call forwarding is done entirely by the home switch (the switch the customer is connected to). Any customer interactions to set, change, or delete a forwarding number occur with the subscriber (customer) accessing directly the switch. Such a system is usually simple, but the service provide by that system is “as is”, and cannot easily be modified or customized.
AIN-based call forwarding services involve a trigger and a query/response from a service control point (SCP). Such a system can be modified and customized more easily, but additional resources are often needed such as a trigger in the switch. Typically, once a trigger is provisioned on a customer's line, the trigger cannot be used for multiple services. That is, the trigger can only be mapped to a single service on the SCP. Depending on what the service does, additional resources may be required such as the involvement of a service node (SN). For example, as with so called “flexible call forwarding”, a service node primarily is used to play announcements and to collect digits from the customer to change call forwarding settings, but usually it is not used during call processing. Accordingly, disadvantages of an AIN-based system involve the use of other resources such as triggers, SCP, and service node, plus additional trunking services.
Therefore, there is a need in the art for an alternative number ringing system that can support the dialing of more than two alternative numbers associated with a main telephone number. The system should not rely upon the resources of an Advanced Intelligent Network's Services Node. The system also should ring the alternative numbers in a predefined sequence maintained in the call list, so that only one alternative number is rung at a time. The system also should enable the easy configuration of the call list by a subscriber and should enable the use of multiple call lists.